HA = High Availability AP = AP in the CAP theorem, which states that in a distributed system you must either choose consistent and Partition tolerant (CP) or A

HA = High Availability AP = AP in the CAP theorem, which states that in a distributed system you must either choose consistent and Partition tolerant (CP) or Available and Partition tolerant (AP), sort of the "heisenberg uncertainty theorem" of distributed system (you can't have CA because for practical purposes the "distributed" constraint implies "partition tolerant").